docs: def query_filter(query):
      """Translate a query-style string to a 'filter'.
  
      Query can be the following formats:
  
      Case Insensitive
        'value' OR '*= value'    Contains
        'value*' OR '^= value'   Begins with value
        '*value' OR '$= value'   Ends with value
        '*value*' OR '_= value'  Contains value
  
      Case Sensitive
        '~ value'   Contains
        '!~ value'  Does not contain
        '> value'   Greater than value
        '< value'   Less than value
        '>= value'  Greater than or equal to value
        '<= value'  Less than or equal to value
  
      :param string query: query string
  
      """
      try:
          return {'operation': int(query)}
      except ValueError:
          pass
  
      if isinstance(query, string_types):
          query = query.strip()
          for operation in KNOWN_OPERATIONS:
              if query.startswith(operation):
                  query = "%s %s" % (operation, query[len(operation):].strip())
                  return {'operation': query}
          if query.startswith('*') and query.endswith('*'):
              query = "*= %s" % query.strip('*')
          elif query.startswith('*'):
              query = "$= %s" % query.strip('*')
          elif query.endswith('*'):
              query = "^= %s" % query.strip('*')
          else:
              query = "_= %s" % query
  
      return {'operation': query}